1. Field
One or more example embodiments relate to an electrolyte for a lithium battery and a lithium battery including the electrolyte.
2. Description of the Related Art
Lithium batteries are used as power sources for portable electronic devices such as video cameras, cell phones, and laptop computers. Rechargeable lithium secondary batteries have an energy density per unit weight that is about 3 times higher than that of conventional lead storage batteries, nickel-cadmium batteries, nickel-hydride batteries, nickel-zinc batteries, or the like, and may be rapidly charged.
Lithium batteries operate at a high driving voltage, and thus, an aqueous-based electrolyte solution that is highly reactive with lithium should not be used in the lithium batteries. Generally, a lithium battery uses an organic electrolyte. The organic electrolyte is prepared by dissolving a lithium salt in an organic solvent. An example of an organic solvent (e.g., a preferable organic solvent) is one that is stable at a high voltage, has high ion conductivity and permittivity, and has a low viscosity.
As an example of the lithium salt, LiPF6 is mainly used. However, a reaction between LiPF6 and the organic solvent of the organic electrolyte causes depletion of the organic electrolyte and produces a large amount of gas. When a carbonate-based non-aqueous polar solvent is used as the organic solvent, a lithium battery undergoes an irreversible reaction using an excessive amount of charge during charging/discharging of the battery, due to a side reaction between an electrolytic solution and a negative electrode/positive electrode. A passivation layer, such as a solid electrolyte interface (SEI) layer, is formed on a surface of a negative electrode by the irreversible reaction. The SEI layer reduces or prevents decomposition of an electrolytic solution and serves as an ion tunnel during charging/discharging of the lithium battery. When the SEI layer has high stability and low resistance, lifespan of the lithium battery may be improved.
In regard to stabilization of the SEI layer, various types or kinds of additives are used. However, a conventional SEI layer formed by using an additive is easily deteriorated at a high temperature, and thus, the stability of the conventional SEI layers is reduced at a high temperature.